Thalassianthus aster is a sea anemone (family Thalassianthidae) found in shallow Indo-Pacific reef environments, forming a distinctive star-shaped oral disc with radiating rows of tentacles organized in a pattern unique among actiniarians. The species inhabits sandy and rubble substrates at the base of reefs where it partially buries its column. Like other thalassianthids, it may host commensal shrimps and fish. Genomic data have been generated for this species and are available in public databases, enabling comparative studies of cnidarian evolution and ecology.